A polishing process, such as a chemical mechanical polishing (CMP) process, is typically used in the formation of an array, such as a memory array, to provide a planar surface to facilitate subsequent processing. During formation of the array, a CMP process is used to provide a planar surface by polishing materials, such as polysilicon and oxide, that have different polish rates (i.e. the rate of removal of the material during the polishing process). This difference in polish rates between the materials in the array during the CMP process can cause undesirable array erosion, which can significantly increase for high-density arrays.
For example, during formation of a high-density array, such as a memory array having a polysilicon segment density greater than approximately 75.0 percent, a conventional CMP process can cause substantial edge array erosion, which can be approximately 100.0 Angstroms or greater. By way of background, in a memory array, edge array erosion refers to the difference between the thickness of a polysilicon segment near the center of the array and the thickness of a polysilicon segment at the edges of the array.
In a conventional CMP process, undesirable array erosion can be reduced by utilizing conventional techniques such as decreasing the pliantness of the polishing pads and/or adjusting the rotary tool parameters used in the CMP process. However, in a conventional CMP process, the conventional techniques discussed above only provide a minimal reduction in edge array erosion in high-density arrays, such as memory arrays having a polysilicon segment density greater than approximately 75.0 percent, caused by a conventional CMP process.
Thus, there is a need in the art for a method of polishing a high-density array, such as a high-density memory array, that provides a significant reduction in undesirable edge array erosion.